A Cyclic Vicinal Bis(tetraketone) and Structural Investigations of Formoins

Abstract

Investigations of simple formoins such as 2,5-bis(1,1-dimethyl-2-phenylethyl)-2,4-dihydroxyfuran-3(2H)-one (17), benzoylformoin (18), p-toluoylformoin (19), pivaloylformoin (20), and the 2,4-dihydroxy-2,5-bis(heterocycl-2-yl)furan-3-ones 21−23 (heterocycle = furan, thiophene, selenophene) by NMR spectroscopy in DMSO showed the dihydroxyfuranone skeleton and not an enediol structure. The formoin 17 was oxidized to the corresponding tetraketone 10. The intermolecular double benzoin condensation of 1,4-bis(2,2-

Experimental study on the reaction pathway of α‐haloacetophenones with nucleophiles: direct substitution or carbonyl addition?

“…It is interesting to note that the NMR spectrum of dimer 5 varied depending on the solvent, indicating that this compound exists as 5 in CDCl 3 and as 5' in DMSO‐d 8 . Similar phenomenon has been reported for analogous compounds in the literature …”

2-(2-Thienyl)quinoxaline

“…A light-brown plate that displayed homogeneous birefringence was mounted for diffraction studies. 1 H NMR and UV-vis spectroscopies, as well as melting points of the title compound, agree with literature values (Peter et al, 2004). (Watkin, 1994, Prince, 1982 [weight] = 1.0/[3.05T 0 (x) + 3.88T 1 (x) + 0.969T 3 (x)], where x = F calc /F max (Á/) max = 0.001 Á max = 0.58 e Å À3 Á min = À0.80 e Å À3 Table 1 Selected geometric parameters (Å , ).…”

“…A light-brown plate that displayed homogeneous birefringence was mounted for diffraction studies. 1 H NMR and UV-vis spectroscopies, as well as melting points of the title compound, agree with literature values (Peter et al, 2004(Peter et al, or?? 1995.…”

A General Strategy for Synthesis of Heterocyclic Hemiketal‐Containing α,β‐Unsaturated Ketones from Ynediones

“…It is noteworthy that the product 3(2 H )‐furanone contains a highly sensitive hemiketal unit similar to d ‐fructose, which usually exists as a mixture of different isomers. However, during our structural investigation on the product 2‐hydroxy‐2,5‐diphenylfuran‐3(2 H )‐one, 2 a was the sole isomer detectable in [D 6 ]DMSO whose ring structure could be opened and isomerized to a single enol, allowing the formation of 5 with a characteristic hydroxy peak in the 1 H NMR spectrum when in CDCl 3 (Scheme ) . The tautomerism between 2 a and 5 should involve enol 4 , which was probably the intermediate of the reaction process toward 3(2 H )‐furanone, resulting from the addition of water to ynedione 1 a .…”